Search PubMed⌕ Search

Biomedical subjects

A Axelsson

Publications and source records attributed to A Axelsson.

198 records · Page 11Linked to original sources
PubMedDate not supplied

Noise effects on the cochlear vasculature in normotensive and spontaneously hypertensive rats.

The cochlear vessels and the distribution of red blood corpuscles were studied in normotensive (N) and spontaneously hypertensive (SH) rats with and without noise exposure. The evaluation was made in a double blind manner. Ten N-rats and ten SH-rats were exposed to noise for 8 weeks and terminated immediately thereafter. The noise consisted of a 2 kHz broad noise band swept from 3 kHz to 30 kHz with a resultant equivalent sound level of 100 dB (lin) 10 h. Seven of 84 vascular parameters differed statistically at the 1% level between N- and SH-rats, and 8 and 10 parameters respectively differed for N- and SH-rats as a result of noise exposure. The observations were interpreted as indicative of a precapillary sphincter constriction in the radiating arterioles of the external wall with an upstream relative stasis and a downstream relative lack of blood, both in N- and SH-rats. In the spiral lamina the observations were interpreted as signs of a decreased blood flow after noise exposure, both in the N- and SH-animals, and most marked in the SH-animals after noise.

Animals↗
PubMedDate not supplied

The effect of noise and carbogen on cochlear vasculature.

Histological measures of cochlear vasculature and blood flow were examined in 24 guinea pigs. Six animals were exposed to white noise at 120 dB SPL while breathing carbogen (10% CO2 and 90% O2) for 30 min. Six subjects were noise exposed while breathing air. Six breathed carbogen without noise exposure and six served as unexposed air-breathing controls. The statistically significant results indicate that noise resulted in reduced blood supply to the cochlea and that carbogen increased cochlear blood flow. When animals were exposed to both noise and carbogen, carbogen tended to counteract the reduced blood supply effects of noise.

Animals↗
PubMedDate not supplied

The laser Doppler: a non-invasive measure of cochlear blood flow.

The present investigation demonstrates the utility of the laser Doppler flowmeter to provide a measure of cochlear blood flow dynamics. Cochlear and cutaneous blood flow were compared with arterial blood pressure during and following exposure to Angiotensin II, 5% carbon monoxide, 100% oxygen, mannitol, and saline. The observations indicate that: 1) cochlear blood flow generally parallels cutaneous blood flow; however, 2) when cutaneous beds vasoconstrict (e.g., AII, alpha-agonists), cochlear blood flow parallels blood pressure; and, 3) under the influence of agents that affect peripheral and central circulation (5% CO, 100% O2), cochlear blood flow may dissociate from cutaneous blood flow and blood pressure. The implications of these findings are discussed in terms of local control mechanisms that may be involved in the inner ear vasculature.

Angiotensin II↗
PubMedDate not supplied

The effects of fatal hemorrhage on the cochlear vasculature.

The condition of the cochlear vasculature was evaluated in 7 normal guinea pigs subsequent to fatal aortic hemorrhage. The cochleas were prepared for histological analysis using a soft surface preparation technique. The data analysis revealed two statistically significant differences: an increase in the number of aggregations and plasma gaps in the vessel at the vestibular membrane ( VSVM ) and in the vessel of the spiral prominence ( VSSP ). In eight instances, a statistical tendency toward a difference was demonstrated. On the whole, the changes observed were small, scattered and inconsistent and were interpreted as indicative of no local circulatory response to hemorrhage. These findings suggest that the cochlear vasculature is either controlled by a marked autoregulation or that histological evidence of a sympathetically mediated vasoconstriction may be counteracted by an elevated PCO2 level causing vasodilation of the constricted inner ear vessels during a state of O2 deficiency. Further, it is proposed that these same mechanisms may also account for the relatively discrete changes seen in the vasculature following noise exposure.

Animals↗
PubMedDate not supplied

The recovery of vascular changes following brief noise exposure.

Histological measures of cochlear vasculature and blood flow were examined in 20 guinea pigs. Sixteen were exposed to octave band noise at 120 dB SPL for 30 min and then permitted to survive after the exposure for 6 h, 18 h, 48 h, or 4 weeks (N = 4 in each group). Control animals were exposed to the laboratory and apparatus but not to the noise and then sacrificed after 48 h (N = 2) or 4 weeks (N = 2). Statistically significant results indicate that the noise exposure resulted in reduced RBCs in the cochlea for animals permitted to survive 6 to 18 h after the noise exposure. These changes, however, were no longer apparent in animals which were permitted to survive 48 h or 4 weeks after the noise exposure. The vascular sequelae of 30 min exposure to 120 dB octave band noise appear to recover within a few days of the exposure.

Animals↗
PubMedDate not supplied

Is there a relationship between hypercholesterolaemia and noise-induced hearing loss?

Many investigators who have analysed the possible correlation between hearing loss and high serum cholesterol levels have found that hearing appears to be influenced by high blood lipids. Noise, as is well known, also influences hearing, particularly at high frequencies. It increases serum cholesterol levels during short-term experiments. The present investigation addresses the question of a possibly increased ototraumatic influence by the combination of high serum cholesterol levels and occupational noise exposure. Seventy-eight 50-year-old men with high serum cholesterol levels from a WHO study were compared with 75 50-year-old men who were randomly selected from the same WHO material. Group mean audiograms showed that hearing was similar in both groups, with a moderate high frequency hearing loss having a configuration suggestive of a noise-induced hearing loss. Analysis of the individual histories and the pure-tone audiograms showed that noise was the most predominant factor influencing hearing at any specific frequency or combination of frequencies. There was a statistically significant tendency for the high-cholesterol group that had suffered the most noise exposure, to have a high-frequency hearing loss. There was also a tendency for the low-cholesterol group to have a high-frequency loss if they had been excessively exposed to occupational noise. No further correlations were found. The present results indicate a slightly increased risk of acquiring a high-frequency sensorineural hearing loss for people who work in noisy environments and have high serum cholesterol levels.

Audiometry, Pure-Tone↗
PubMedDate not supplied

Cochlear blood flow studied with microspheres. A comparison between two different modifications of the microsphere method.

In albino rabbits, spontaneously hypertensive rats, and guinea pigs, cochlear blood flow was measured with the microsphere method, using radioactively labelled microspheres technique and a gammaspectrometer. This 'conventional' microsphere method was compared with a new technique for measurements of cochlear blood flow: a modification of the 'radioactive' microsphere technique and the soft surface specimen technique. Values obtained for cochlear blood flow by the two different methods were similar. Consequently, the microsphere surface technique is a suitable alternative to the classical radioactive microsphere method for blood flow determinations in the cochlea.

Acid-Base Equilibrium↗
PubMedDate not supplied

The early postnatal development of the cochlear vasculature in the gerbil.

The blood vessels of the cochlea were studied from birth up to adult age in the gerbil. Even at birth the principal vascular arrangement could be identified in the external wall. However, the early circulatory mainstream appeared even more predominantly radial apico-basal over radiating arterioles-arteriovenous anastomoses-collecting venules than at later stages. At birth, only small sections of capillaries could be observed in the stria vascularis. Stria vascularis achieved its adult vascular appearance rapidly between 8-10 days after birth (DAB). The rapid development of stria vascularis immediately preceded the development of cochlear function and may have been related to the development of the ionic composition of endolymph. At birth the vessel of the basilar membrane showed many large vascular connections with the collecting venules in the scala tympani of the external wall but very few supplying and draining ramifications on the medial side of the vessel. This suggests that the vessel of the basilar membrane originates from the external wall vessels, not from the spiral lamina vessels as has previously been supposed. The peripheral vascular connections degenerated rapidly after birth. The vessel, being very large at birth, degenerated completely by 15 to 20 DAB, ultimately disappearing in the basal turn. The degeneration suggests that its major importance may be during embryonic stages, with great probability for the development of the organ of Corti.

Aging↗
PubMedDate not supplied

Acute acoustic trauma.

Acute acoustic trauma is a clinical condition with immediate persistent hearing loss after impulse or blast wave noise. This condition is not well recognized in occupational medicine and probably not even in otolaryngology. We report 52 cases of acute acoustic trauma including information concerning the traumatic event. Most cases occurred within military service and in the shipbuilding industry. Except for immediate hearing loss, many patients experienced tinnitus and some pain and hyperacusis. Relatively few patients report immediately. Most patients have been met by a nihilistic approach to therapy, in most cases due to the fact that patients report long after the trauma. The aim of the report is to focus attention on this clinical condition, since there is some indication that the final outcome may improve if patients are taken care of and treated early.

Acute Disease↗
PubMedDate not supplied

Histological measures of cochlear blood flow. A validation study.

Cochlear blood flow in guinea pigs was assessed using histological assessment of various red blood cell and vessel lumen parameters. Cochlear blood flow was either enhanced by administration of carbogen or inhibited by induced positive airway pressure. The resulting enhancement or reduction of blood flow in the cochlea was verified by laser Doppler velocimetry. The results generally indicate that the two measures of cochlear blood flow agree. This agreement was especially apparent when histological parameters of the vessel lumen were considered and when external wall vessels were evaluated.

Animals↗
PubMedDate not supplied

Changes in cochlear blood flow during acoustic stimulation as determined by 14C-iodoantipyrine autoradiography.

Local blood flow was measured in the tissues of the cochlea using the [14C]iodoantipyrine autoradiographic technique. Flow observed without acoustic stimulation was compared with that seen during exposure to wide-band noise at 85 or 105 dB SPL. Compared with the unexposed cochlea, substantial increases in blood flow were observed during exposure to 85 dB SPL noise in the spiral ganglion, VIII nerve and spiral lamina. Little or no change was noted in external wall structures. These results are consistent with changes in cochlear metabolism which have been reported previously using similar techniques, suggesting that increases in blood flow may be linked to increases in local metabolism. No changes in blood flow were measured during exposure to 105 dB SPL noise. This result is similar to those of other investigators using potentially damaging intensities of acoustic stimulation.

Acoustic Stimulation↗
PubMedDate not supplied

Observations of cochlear microcirculation using intravital microscopy.

The guinea pig cochlea was prepared for visual observation of blood vessels using fluorescence intravital microscopic techniques. Measurements were made of the lateral wall vessels in the third cochlear turn and of the basilar membrane and lateral wall vessels in the first turn. A stable and consistent pattern of flow was observed under a variety of manipulations, including blood pressures of less than 20 mmHg. The rationale for the choice of observation areas in the cochlea and the specific vessel types studied at these locations are discussed. The change in blood velocity in cochlear blood vessels during pentoxifylline perfusion and during exsanguination are described.

Animals↗
PubMedDate not supplied

Does pop music cause hearing damage?

Relatively few investigations have so far reported on the hearing in pop musicians. In summary, these have shown a sensorineural hearing loss in 5%. This study was carried out on 83 professionals working with pop music. Depending upon how hearing loss is defined, we found a sensorineural loss in 13-30% of the pop musicians. Hearing losses were slight. It appears that the risk for hearing damage for the audience is small. A limit for presentation of the music at 95 dB (A) is suggested as a compromise satisfying both audiologists and audience.

Adolescent↗
PubMedDate not supplied

Ginkgo biloba extract for the treatment of tinnitus.

Previous studies have shown contradictory results of Ginkgo biloba extract (GBE) treatment of tinnitus. The present study was divided into two parts: first an open part, without placebo control (n = 80), followed by a double-blind placebo-controlled study (n = 20). The patients included in the open study were patients who had been referred to the Department of Audiology, Sahlgren's Hospital, Göteborg, Sweden, due to persistent severe tinnitus. Patients reporting a positive effect on tinnitus in the open study were included in the double-blind placebo-controlled study (20 out of 21 patients participated). 7 patients preferred GBE to placebo, 7 placebo to GBE and 6 patients had no preference. Statistical group analysis gives no support to the hypothesis that GBE has any effect on tinnitus, although it is possible that GBE has an effect on some patients due to several reasons, e.g. the diverse etiology of tinnitus. Since there is no objective method to measure the symptom, the search for an effective drug can only be made on an individual basis.

Adult↗
PubMedDate not supplied

Acupuncture in the management of tinnitus: a placebo-controlled study.

The present study was performed on 20 patients randomly selected from a large group with noise-induced tinnitus in order to investigate the effect of acupuncture on their tinnitus. The patients were divided into two groups. One group first received classical Chinese needle acupuncture for 5 weeks, and the other was given a placebo procedure; after a 2-week interval, the procedures were reversed. A single-blind cross-over design was used. Acupuncture was given by a Chinese otolaryngologist around the ear as well as at distal points on the extremities. Placebo consisted of mock electrical stimulation via surface electrodes connected to a Chinese electro-acupuncture stimulator which delivered a weak sound and a light flash at a frequency of 2 Hz but no current to the surface electrodes. The effect was evaluated by the use of visual analogue scales. No significant difference between acupuncture and placebo was found in annoyance, awareness or loudness of the tinnitus. Many patients indicated a preference for acupuncture due to unspecific effects such as improved sleep, decreased muscle tension and improved blood circulation. It is concluded that acupuncture has no specific alleviating effect on noise-induced tinnitus.

Acupuncture Therapy↗
PubMedDate not supplied

Tinnitus information: a study by questionnaire.

The aim of the present study was to improve the information for patients with tinnitus. The investigation consists of three parts: a pilot study where 24 slightly informed tinnitus patients as well as 17 well-informed tinnitus patients and 9 audiological professionals suggested contents for a tinnitus information pamphlet. The second part consisted of scoring of the 74 most common suggestions by 36 of the original 50 people. The answers were graded according to importance. Three available tinnitus information folders from Sweden, Germany and the USA were also studied and taken into account in preparing recommendations on content and size for a tinnitus information pamphlet. This should probably not exceed 2500 words, and 35 items of information.

Adult↗